Many food loaf products, ranging from bologna and sausage through meat loaf, ham loaf, and other food loaf products, are initially manufactured in long loaves, usually ranging from two to six feet in length. These food loaves are then machine sliced and packaged prior to shipment to retail outlets. A food loaf slicing machine employed in this field should have a high rate of production, preferably in a range of at least two hundred to one thousand slices or more per minute. It is essential that the slices be cleanly and smoothly cut. To avoid undue waste, it is also important to maintain precise and accurate control of the weight of the individual slices as well as the weight of each stack. Continuous operation of the slicing machine is virtually essential, since any interruption required for loading additional loaves or for any other purpose materially reduces the production rate.
In one commercial food loaf slicing machine, each food loaf is fed generally downwardly, by a conveyor mechanism, into a slicing station. As the end of the loaf advances into the slicing station, it is cut off by a rotating orbiting circular knife. The orbiting motion of the knife, which swings the knife into and out of the slicing station, determines the slice rate or production rate of the machine. The rotation of the knife provides a clean slicing action. Machines of this general type, though basically advantageous as compared with other slicing mechanisms, nevertheless present continuing difficult problems.
Different loaf materials may have very different slicing characteristics which require substantially different knife rotation speeds, even though the slicing (orbiting) rate may be the same. Thus, in a slicing machine of the kind that employs a knife having both orbital and rotary motions, with the orbital rate determining the slice rate and the rotational rate determining the cutting rate, a soft material such as bologna or soft sausage may be cut most smoothly and cleanly at a low rotary cutting speed whereas a more dense high muscle content loaf such as a ham loaf may require a much higher rotary speed to achieve comparable results. The optimal cutting rate, relative to the slicing rate, is a matter for empirical determination for virtually any kind of loaf. Consequently, a high production food loaf slicing machine may require a wide range of variation in the ratio of cutting (rotary) speed to slicing (orbital) speed. Although previously known machines have provided for some variation in this regard, the variation has usually been quite limited, particularly because of the common practice of driving the orbital and rotary motions of the knife from a single motor.
To achieve optimally clean, smooth slices, in a high production food loaf slicing machine using an orbiting rotary knife, there should be a working surface, against which the knife works, that matches the contour of the knife edge and its movement through the slicing station. This is difficult to achieve in the first place and becomes virtually impossible to maintain, when utilizing a pre-formed metal working surface, due to variations in the knife diameter and knife edge contour that occur when the knife is sharpened.
As manufactured, sausages and other food loaf products are not notable for precise accuracy in their cross-sectional dimensions throughout the lengths of the loaves. Any variation in loaf cross-section produces a corresponding variation in the weight of the individual slices, if the slice thickness is not adjusted to match the cross-sectional changes. A variation of this kind cannot be effectively corrected by the common expedient of weighing each stack of slices as it leaves the slicing machine; it is then too late.
Even though the end of each loaf may be cut off (trimmed) before the loaf is loaded into a high production slicing machine, it is virtually impossible to cut the loaf ends to match precisely with the cutting configuration of the slicer, particularly when using a combination rotary and orbital knife. Thus, when the slicing machine operates continuously, it is a virtual certainty that a limited number of malformed slices will be produced during the transition point from one loaf to another. Usually, this results in a stack of slices that is out of weight tolerance and can be rejected on that basis, but some stacks containing malformed slices may pass through the machine undetected on the basis of weight variations. Furthermore, it is quite difficult to hold the small butt end of a loaf that has been almost completely sliced in accurate alignment in the slicing equipment while that butt portion is being sliced. Of course, the production of substantial numbers of malformed slices leads to material waste that is economically disadvantageous.
In any high production meat loaf slicing machine, the weight of the individual slices and the weight of each stack of slices is critically dependent upon the rate at which the food loaf is fed into the slicing station. The minimum weight for each stack presents an absolute requirement in order to avoid violations of packaging laws. Consequently, it is customary to adjust the slicing machine to assure the production of stacks that always exceed the minimum weight that will be marked on the completed packages. The built-in system waste from this source can be an appreciable adverse factor in the economics of a packaging operation. The smaller the increments for control of the rate at which the loaf is fed into the slicing station, the greater the potential for economical operation.